1. Field of the Invention
The present invention relates to an abrasive sheet of a nonwoven fabric. More particularly, the present invention relates to an abrasive sheet able to be used in a texturing process in the production of a magnetic recording medium.
2. Description of the Related Art
A magnetic recording medium, such as a magnetic diskette, is produced by applying a non-magnetic plating, such as an anodized aluminum or nickel-phosphorus plating, to a substrate, such as an aluminum alloy substrate to form a non-magnetically plated substrate; carrying out a texturing process on a surface of the non-magnetically plated substrate; and then sequentially coating thereon a primary layer (generally, a chromium layer or the like), a magnetic thin layer (generally, a cobalt-alloy layer or the like), and a protective layer (generally, a carbonous layer or the like). The space between the magnetic diskette and a magnetic head, i.e., a flying height, must be as small as possible. Therefore, the magnetic diskette must not have any projections from the surface thereof. Namely, the surface must be smoothed.
If the surface of the magnetic diskette is too smooth, however, the magnetic head cannot be levitated because the magnetic head adheres the diskette. To avoid this, fine grooves are formed on the surface of the non-magnetically plated substrate, i.e., a texturing process is carried out. This texturing process comprises grinding the surface of the non-magnetically plated substrate to uniformly form fine scars, i.e., a texture.
Hitherto, as an abrasive material used in the texturing process, for example, a nonwoven fabric prepared by fixing fibers having a diameter of about 3 .mu.m with urethane resin, a woven fabric composed of fibers having a diameter of about 5 .mu.m, or a flock-printed sheet carrying thereon a number of short fibers having a diameter of about 14 .mu.m are known.
However, when the nonwoven fabric prepared by fixing fibers having a diameter of about 3 .mu.m with urethane resin is used to abrade the surface of the substrate, large scratches appear on the surface of the substrate, caused by a lack of freedom of the fibers. Further, urethane resins drop off and adhere to the substrate. Accordingly, the surface of the substrate becomes nonuniform. The woven fabric composed of fibers having a diameter of about 5 .mu.m also causes large scratches to appear on the surface of the substrate, also caused by a lack of freedom of the fibers. Further, the fibers on the flock-printed sheet are arranged perpendicular to the surface of the substrate, and thus are liable to cause large scratches to appear on the surface of the substrate.